In recent years, such an occasion has increased that a reflection polarizer is used in a liquid crystal display device. The reflection polarizer reflects light of a particular linear polarization component, said transmits light of a component orthogonal to the particular linear polarization component. As the reflection polarizer, for example, there are a polarizer comprised of a layered product of birefringent resin, and a wire grid type polarizer in which a plurality of conductive materials (metal thin wires) extends parallel on a transparent substrate. Further, as a polarizer that reflects or transmits light of a particular circular polarization component instead of reflecting or transmitting light of a linear polarization component, there is also a polarizer comprised of cholesteric phase liquid crystal. Among the polarizers, as a reflection polarizer which has high polarization transmittance to enable light of a desired linear polarization component to be obtained, and is able to make light of a linear polarization component orthogonal to the desired linear polarization component low polarization transmittance (high polarization reflectance), the wire grid type polarizer receives attention. In addition, the ratio of transmittance between light of two actually orthogonal linear polarization components is referred to as an extinction ratio of transmitted light.
Generally, in the case where a pitch of metal thin wires is sufficiently smaller than a wavelength of incident light, among the incident light, the wire grid type polarizer has a property of transmitting light of a linear polarization component having an electric field vector orthogonal to an extension direction of the metal thin wires while reflecting light of a linear polarization component having an electric field vector in the extension direction of the metal thin wires.
As a method of preparing the wire grid type polarizer, such a method is known that a thin film made of a conductive material is prepared on a substrata surface, a polymer layer is formed on the thin film, then a pattern is formed on the polymer layer using a mold having a pattern prepared by an interference exposure method, electron beam lithography method or the like, and that metal thin wires are prepared by a dry etching method or the like on the thin film made of the conductive material using the pattern on the polymer layer (Patent Document 1). Further, such a method is also known that a conductive material is deposited on the side surface of a substrate convex portion on a concavo-convex-shaped substrate using an oblique deposition method (Patent Document 2). The former method needs an expensive manufacturing apparatus required for interference exposure, electron beam lithography, dry etching and the like and has the problem of low productivity. Meanwhile, the latter manufacturing method is capable of simplifying the process, thereby providing high productivity, making the contact area of the conductive material and the substrate convex portion large since the conductive material is deposited on the side surface of the substrate convex portion, and decreasing losses of the conductive material due to external forces or the like. Hereinafter, such a wire grid type polarizer is referred to as a wire grid polarizing plate.
The wire grid polarizing plate is a reflection polarizer allowing high polarization reflectance, thereby enables high luminance to be obtained by light recycling, and in the respect of little generation of heat generated from absorption of light, is suitable for liquid crystal display devices.